The invention generally relates to methods and systems for classifying rollover events or conditions associated with vehicles. More specifically, the invention relates to using acceleration information and vehicle orientation information to determine a type of vehicle rollover event.
It is known that vehicles, such as automobiles, are capable of rolling over under certain driving and environmental conditions. In the event that a vehicle does or is about to rollover, vehicle occupants are at risk of serious injury. To reduce the risk of injury, a vehicle may include a rollover sensing system that senses when a vehicle rollover event occurs or senses the occurrence of conditions that are indicative of a rollover event occurring. Upon sensing the relevant event or conditions, the system activates safety devices such as seat belt retractors or airbags. Regardless of their exact architecture or design, rollover detection systems are often explained in terms of detecting the occurrence of a rollover event before the vehicle has fully rolled over. This convention is followed in the discussion below.
One known rollover system includes a controller that receives information from a plurality of sensors including a roll rate, a yaw rate, a vehicle speed, and a lateral acceleration sensor. The vehicle roll angle is determined by integrating information from the roll rate sensor and a cant compensation is determined from the lateral acceleration, vehicle speed, and yaw rate data. The controller uses sensor information as axis parameters for a two-dimensional map, or mode map, and determines which region of the map contains the present state of the vehicle.
Other known systems also implement mode maps for detecting lateral overturning. For example, some employ multiple sensors and two-dimensional maps that utilize the roll angle and rolling angular speed as axis parameters. A determination of an overturn possibility may be based on the location of a hysteresis path traced by the roll angle and rolling angular inputs. Some of these systems include a threshold value line that designates regions of lateral overturn and lateral non-overturn and may be shifted in response to a rolling resonance. In addition, some systems include an occupant position sensor and utilize an output signal to control an occupant protection system.
Although systems for detecting a vehicle rollover event exist, they are not completely satisfactory. Prior systems and methods are excessively complex and do not possess, or are limited in, the ability to timely determine rollover events while, or in addition to, compensating for the effects of gravity. Accordingly, a need exists for a system and method to classify a type of vehicle rollover event that includes calibrateable and less complex algorithms, which compensate for gravitational effects and provide quicker and more reliable rollover event determination.
In one embodiment, the invention includes a method for detecting a rollover condition of a vehicle where lateral acceleration information, vertical acceleration information, and roll angle information is acquired and processed. In one embodiment, the roll angle information is used in compensating the acceleration information for the effects of gravity. The compensated acceleration information is compared with one or more thresholds. The comparison is used to change a counter and additional threshold comparisons are used to determine the vehicle condition or rollover type. In some embodiments, the thresholds and counter variables are calibrateable.
In another embodiment, a vehicle has a frame and one or more sensors that are operable to sense an acceleration of the vehicle. A processor is coupled to the vehicle and receives information from the one or more sensors. The processor includes one or more modules, such as a gravity compensation module, an acceleration counter module, and a classification module. In addition, the processor is operable to compensate the information received from the one or more sensors based on an angle of the vehicle, change a value associated with a counter in response to the compensated information, and determine a type of vehicle condition based on the value associated with the counter.
Additional objects and features of the invention are illustrated in the drawings and provided in the subsequent disclosure.